This application claims the benefit of co-pending German Patent Application No. 199 63 097.6 entitled xe2x80x9cZange zum Verpressen eines Werkstxc3xcicksxe2x80x9d filed on Dec. 24, 1999.
The present invention generally relates to pliers for crimping work pieces. More particularly, the present invention relates to pliers being operable with one hand and serving to apply great crimping forces onto the work piece in a few crimping steps.
Pliers of this kind are also called crimping pliers or pressing pliers. Depending on the design of the work piece, especially in case of fittings, tubes and the like to be crimped, substantial pressing forces have to be applied onto the work piece. On the other hand, such work pieces may have comparatively great dimensions. Consequently, the crimping die being formed by two dies should have a great opening in the opened position of the pliers to be able to move the two dies over the work piece to be crimped in the opened position of the pliers. At the beginning of the closing movement of the pliers, there usually are no or at least no substantial pressing forces to be overcome. Contrarily, the pressing forces to be applied during the actual crimping movement of the work piece are substantial.
Pliers for crimping work pieces are known from German patent application DE 197 09 639 A1. The pliers include two handles being movable with respect to one another by one hand. A joint supports two pivot jaws. One of the two pivot jaws is connected to a stationary handle to form a stationary portion of the pliers. The other pivot jaw is pivotally connected to the stationary portion of the pliers by the joint. The pliers include separated dies forming a crimping die. A locking mechanism is arranged between the stationary handle and the movable handle, and it serves to reach a defined end position of the separated dies. The handles may first be reopened after one crimping process has been finished, after the end position has been reached and after the locking mechanism has released the handles. A pressure lever is arranged between the handles, and it is pivotally supported by the supporting joint. The pressure lever together with a section of the movable handle forms a toggle lever drive. This sole pressure lever is supported in a supporting joint including an eccentric surface allowing for an adjustment of the effective length of the pressure lever. The adjustability of the pressure lever serves to compensate work tolerances to exactly associative a closing position of the handles with an end crimping position of the pliers. It is also possible to adjust the pressure lever to eliminate wear and tear occurring at the connected joints or the dies. The two dies and the corresponding pivot jaws are designed as one piece. The fixed connection of the combined pivot jaw/die to the stationary handle is disadvantageous. The maximum applicable crimping forces are limited. Additionally, the preciseness of the finished crimped work piece highly depends on the realizable process tolerances with which the elements of the pliers are produced and which are used to assemble the pliers. Consequently, it is necessary to rework the dies of the pliers in many cases. The known pliers include handles made of molded plastic. These handles provide great stability at reduced exactness. Since the material flows, disadvantageous displacements of, for example, prearranged bores cannot be prevented. With the known pliers, the work piece is crimped in one crimping step.
Clamping pliers are known from German patent DE 25 59 656 B2. The clamping pliers include two handles being movable with respect to one another. Two pivot jaws are rotatable about a common joint. One of the pivot jaws is connected to a stationary handle to form a stationary pliers portion. The other pivot jaw is pivotally connected to the stationary pliers portion by the joint. A pressure lever is arranged between the two handles. The pressure lever is pivotal about a supporting joint and, together with a section of the stationary handle, it forms a toggle lever drive. To adjust the effective length of the pressure lever despite the fixed connection of the pressure lever at both ends at the handles, at least one of the supporting joints includes an eccentric tappet including different angle positions to adjust the kinematics of the clamping pliers, especially of the end position during the closing movement of the pivot jaws.
German patent DE 25 55 071 C2 additionally shows the application of a locking mechanism being arranged between the pressure lever and the stationary handle to reproducibly attain the defined end position of the pliers.
Clamping pliers including two handles being movable with respect to one another and two pivot jaws being pivotal about a common joint are known from U.S. Pat. No. 2,410,889. Each of the pivot jaws is connected to the associated handle to form a fixed pliers portion therewith. One of the two handles is divided into two portions each forming a lever to crimp the work piece in a few crimping steps. The two portions of the handle are interconnected by a joint to be pivotal with respect to one another. The portion of the handle to be held by the hand of the operator is lengthened in the direction towards the pliers head to extend beyond the joint to form a lever arm serving for transmission. A pulling lever is pivotally connected to the free end of the handle. The pulling lever encloses the two handles, and it is supported at the other handle not being divided. In this way, one portion of the divided handle is coupled to the other handle not being divided in each crimping step in different angle positions changing during the crimping process in a way that the end portions of the two handles facing away from the pliers head may be held and operated by the fingers of one hand in each angle position of each crimping step. Due to the division and support of the one handle at the other handle, there is an additional transmission of the actuation force to be applied by hand.
Briefly described, the present invention provides pliers for crimping work pieces. The pliers include a pliers head, a first pivot jaw being arranged in the region of the pliers head and a second pivot jaw being arranged in the region of the pliers head. A common joint pivotally connects the first and second pivot jaw. A first die is arranged at the first pivot jaw. A second die is arranged at the second pivot jaw. The first die and the second die together form a crimping die for crimping the work piece. A first handle is operatively connected to the first pivot jaw, and it includes an end portion facing away from the pliers head. The first handle is divided into at least a first portion and a second portion. A second handle is operatively connected to the second pivot jaw, and it includes an end portion facing away from the pliers head. The first and second handle are designed and arranged to be movable with respect to one another and to be operable to crimp the work piece in a few crimping steps. The second portion of the first handle is coupled to the first portion of the first handle in a plurality of different angle positions each corresponding to one crimping step in a way that the end portions of the first and second handle may be held and operated by the fingers of one hand of the operator in each angle position of each crimping step. A locking mechanism is designed and arranged to attain a defined closed position of the first and second die. A toggle lever drive includes a plurality of supporting joints and a pressure lever operatively connecting the first and second handle. The pressure lever is supported by the plurality of supporting joints.
The present invention is based on the concept of designing the pliers user friendly and appropriate for applying great crimping forces. It is desired to ensure that the pliers may be used and operated by one hand. This means that the handles need to be designed in a way that they may be grasped by the fingers of one hand of the user already at the beginning of each crimping step and that they may be pressed towards each other during the crimping stroke. On the other hand, it is desired to be able to apply crimping forces of up to 3 to 5 tons and more onto the work piece, even during overhead or narrow working conditions.
In the prior art, it is only possible to apply such great crimping forces with crimping tools including an electrical drive or a hydraulic drive. The pliers according to the present invention are designed to attain these great crimping forces by realizing a plurality of crimping steps or stages.
At least one of the handles is divided into at least two portions each forming a part of the handle. Each part of the handle forms a lever arm. This sum of the lengths of the two lever arms corresponds approximately to the length of the lever arm of the other handle. The two portions of the divided handle are interconnectable and they support each other, respectively, in a different angle position in each crimping step. Thus, the end portions of the two handles facing away from the pliers head may be grasped by the fingers of one hand of the operator in each angle position of each crimping step. The crimping steps result from a change of the angle position of the portions of the divided handle with respect to each other. Generally, it is sufficient to realize two angle positions and, consequently, two crimping steps. However, in case of great requirements, there is the possibility of providing a few crimping steps one after the other. Realizing a few crimping steps means to provide at least two crimping steps up to approximately four crimping steps. In combination with a toggle lever drive, it is ensured that the part of the handle of the divided handle facing away from the pliers head is progressively dislocated with respect to the geometry of the toggle lever drive, especially with respect to the dead center of the toggle lever drive, in each crimping step. The ratio of transmission of the toggle lever drive is used during each crimping step. In this way, the necessary operating forces to be applied manually are kept low.
The novel pliers have a short structural length and a comparatively little weight. The pliers are at least operable by one hand of the user in the crimping steps. This means that the free end portions of the handles at the beginning of each crimping step are located in a position in which the distance between them is less than approximately 110 mm. However, the operator may use both hands to increase the hand forces. In case three crimping steps are realized, both handles may be divided.
The locking mechanism is operable located between the fixed handle and the pivot jaw being pivotal about the joint. The locking mechanism does not transmit crimping forces, but it only serves to reproducibly reach a defined end position of the dies and to attain crimping results of constant quality at a series of work pieces having the same dimensions. The arrangement of the locking mechanism in the pliers is of substantial importance. The jack of the locking mechanism is resiliently movable but stationary. The jack may be arranged at the fixed handle, the locking mechanism preferably including a tooth segment including a low number of teeth having a comparatively great pitch. The tooth segment is arranged at the movable pivot jaw, or at least it is connected thereto. With this arrangement, the pliers are adjustable such that the end position is safely attained in the last crimping step, and that an especially great crimping pressure is reproducibly applied before the pliers may be reopened, for example by a spring. In the completely opened position of the pliers and after the work piece to be crimped has been inserted into the pliers, the pliers may usually not be operated by one hand. However, this is no disadvantage since no crimping forces are applied in this position, but the dies do only have to be closed to surround the work piece. The crimping forces are realized during the crimping steps.
The first portion and the second portion of the divided handle may be designed and arranged to be automatically adjusted to reach the different angle positions between the crimping steps. This means that that the second angle position between the portions of the divided handle is automatically reached and locked after the first crimping step has been finished. It is also possible to choose a semi-automatic design that may depend, for example, on an opening stroke of the handle after the first crimping step. It is preferred to use a spring for this arrangement.
However, the first portion and the second portion of the divided handle may also be designed and arranged to be manually adjustable to reach the different angle positions between the crimping steps. Especially in combination with such a manual adjustment of the two angle positions of the two portions of the divided handle, there are a number of different design possibilities for the person with skill in the art. It is especially simple to design the portions of the divided handle in a way that they may be put together in two different angle positions. A locking mechanism including a ball for securing the positions of the two portions of the divided handle may be used. Additionally or alternately, an elongated hole connection may be arranged to act between the portions of the divided handle to make sure that the portion of the divided handle forming the free end is captivated at the pliers. An elongated hole connection is to be understood as a device including an elongated hole or opening and a pin or bolt engaging the elongated hole.
Another possibility is to interconnect the two portions of the divided handle of the pliers by a joint, on the one hand, and by an elongated hole connection, on the other hand, to be adjustable to alternately reach the two angle positions with respect to each other. The elongated hole connection extends in a transverse direction with respect to the direction of main extension of the two portions of the handle. The elongated hole is located at one portion of the divided handle. A transverse pin or bolt or the like is located at the other portion of the handle. The elongated hole may also be designed as a gate including a plurality of offsets. A locking bolt may be movably guided in one portion of the divided handle, the locking bolt being subject to the pressure of a spring. A stop cooperating with the locking bolt may be arranged at the other portion of the two-part handle. In this way, the angle position being associated with the second crimping step is determined in a semiautomatic fashion when the opening stroke being conducted after the first crimping step has been finished is sufficient.
The pliers may also include a first elongated hole connection and a second elongated hole connection. The two elongated hole connections alternately connect the two portions of the divided handle in two different angle positions. Both elongated hole connections are designed and arranged to allow for a limited movement of the two portions of the handle with respect to one another in their direction of main extension. One of the two elongated hole connections is designed and arranged to allow for a limited movement of the portions of the handle in a direction transverse to their direction of main extension.
It makes sense to arrange the pressure lever to be connected to the portion of the divided handle facing the pliers head. In this way, the same ratio of transmission prevails in each crimping step. Generally, the division or the separation of the divided handle may be realized in way that the portion of the handle facing the pliers head has a lever length being a little less than the lever length of the other portion of the divided handle forming the free end portion.
The locking mechanism may include a tooth segment being fixedly connected to the portion of the divided handle facing the pliers head to be commonly rotated therewith and a locking jack being supported on the pressure lever. With this arrangement, the locking mechanism is arranged at an appropriate location defining the end position of the dies of the pliers. In combination with the use of an eccentric bolt for supporting the pressure lever of the toggle lever drive, the play or looseness prevailing in the joints and the corresponding work tolerances of the elements of the pliers may be adjusted to be very small.
Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and the detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention, as defined by the claims.